Cause:
When there are only standalone Hosts in the datacenter VM prioritization cannot be used.

Solution:
Upgrade to PowerChute Network Shutdown version 4.2

For PowerChute Network Shutdown version 4.1
In a configuration that only includes standalone hose use Automatic VM Startup/Shutdown feature to control the order that VMs are shutdown/started on the individual hosts. See Kbase FA159688
If you have a HA cluster with at least 1 host (normally 2 or more) and some standalone Hosts in the Datacenter PCNS will display VMs for the Standalone Hosts as well as the VMs in the Cluster and those VMs can be prioritized in the PCNS UI.